On YouTube I should look for "Lai Lai Lai" from the Seventies or Eighties. 2 men were the singers. In the meeting-point they have said, it would be by Simon & Garfunkel. I have searched for "simon and garfunkel lai lai lai". And while in the other room there is music and singing with a guitar, in the computer-room I have to check out, if it is this song...